Hydraulic shock absorber



Aw Z 1936.

N. s. FocHT 2,036,623

HYDRALIG SHOCK ABSORBER Original Filed Feb. 21, 1955 3 Sheets-Sheet 1 IIA -uul jg; lllllllm p,... Humm Miri/715.1770071@ April 7, 1936*. s FOCHT y 2,036,623

HYDRAULIC SHOCK ABSORBER Original Filed Fb. 2l, 1935 3 Sheets-Sheet 2 'Q Manin/5.1700111,

April 7, 1936.

. N. s. FocHT l 2,036,623

HYDRAULIC SHOCK ABSORBER 13 4 EHA www `37 3W/MM X M4; in 5.1750101', 26' fr l Patented Apr.- 7, 1936 A' UNI-TED. 4STATES HYDRAULIC' SHOCK ABSORBEB.

, Nevin S. Fooht, Reading, Pa.

Application February 21, 1935, Serial No. 7,610

BenewedFebruary 27, 1936 v 1s claim. (ci. iss-ss) 'I'his invention relates to shock absorbers vfor use on motor vehicles, airplanes, industrial machines and the like, and has generally in view to provide a hydraulic shock absorber, preferablyr but not necessarily of the strut type, operating on the general principle and possessing the `principal advantages of the vane and strut type shock absorbers described and claimed in my prior Patent No. 1,957,452 dated May 8, 1934,' andin 1;) my copending application, Serial No. 691,211.

A special object of the invention is to provide a shock absorber of the type mentioned which, asvcompared with the shock absorbers described and claimed inthe aforesaid applications. is of l5 considerably simplified construction, more readily and easily assembled and of lower production cost.

Another special object of the present invention is to provide a shock absorber of theA type mentioned in which all of the liquid control valves are readily accessible from the` outside of the shock absorber and may readily bev removed for adjustment or other purposes and equally as i readily replaced without disturbing other parts 25 of the shock absorber.

Another special object of the present invention W is to provide a shock absorber of the type mentioned ,having an exceptionally large liquid storage reservoir and further embodying in this connection a construction whereby the possibility of all; pocketsdeveloping within the shock absorber .during its operation is effectively eliminated.

Another special object of the invention `is to provide a shock absorber of the character mentioned embodying a novel combination and arrangement of a minimum number of simple valves to assure desired control of vshocks under all conditions and phases of operation of `Vthe shock absorber.

Another object of the invention is to provide novel means to assure effective purging of air from the pressure chambersof the shock absorber. e

With the foregoing and other objects in view, which will become more fully apparent as the nature of the invention is better understood, the same consists in the novel-features of construc- A tion, combination and arrangement of parts as will be hereinafter more fully described, illustrated in the accompanying drawings and defined in the appended claims. I

In the drawings, wherein like characters of' reference denote corresponding parts in the different views:-

Figure 1 is a central, longitudinal section through a shock absorber constructed in accordance with the invention.

Figure 2 is an enlarged cross-section on the line 2-2 of Fig. 1. v 5

Figure 3 is an enlarged cross-section on the line 3 3 of Fig. 1.

Figure 4 is a section on the line 4 4 of Fig. 3.

Figure 5 is a section on the line 5-5 of Fig. 3; and

Figures 6 and 7 are sectional views similar to Figs. 4 and 5, respectively, illustrating another embodiment of the invention.

Referring to the drawings ,in detail, it will be observed thatthe present shock absorber, accordl5 ing to the practical embodiment thereof illustrated in the present instance, isof the general strut type design shown in my prior application, Serial No. 691,211, and includes a working cylinder I'Il anda piston II for connection, respectively, 20

with a pair of relatively movable elements such, for example, as the axle and the chassis of a motor vehicle. x v 'I'he shock absorber may be disposed for operation either horizontally, or at an inclination to the horizontal, or vertically. In most instances it will be disposed vertically or substantially vertically. For purposes of the present description it will therefore be assumed to be disposed vertically. Surrounding the cylinder I0 is a tube I2 which is of somewhat greater internal diameter than the external diameter of said cylinder. Similarly, a casing lI3 of fsomewhat greater internal diameter than the external diameter of the tube I2 35 surrounds said tube. The cylinder, tube and casing are closed at their ends by upper and lower heads I4 and I5, respectively, the tube I 2 in the present instance being threaded at its ends into said heads and the latter being provided with counter-bores receiving `the ends of the cylinder i I0 and the casing I3, whereby "aid heads and the cylinder, tube and casing are maintained rigidly in assembly with each other, with the cylinder, tube and casing disposed concentrlcally. Thereby, an annular liquid passageway I6 is provided between the cylinder I0 and the tube I2, and an annular liquid reservoir I 'l is provided between 4 K the tube I2 land the casing I3. i

The piston II is reciprocal within the cylinder I0- and its normal position is approximately mid- Y 'way between the heads I4 and I5, dividing the cylinder into upper and lower pressure chambers a and b, respectively. Extending upwardly from saidpiston through the chamber a and through which, at its upper end, carries a combined closure capand attachment element I3 `for connecthe pressure chamber a. Any air contained' tion with one of the elements, such as the axle or vchassis of a vehicle, movements of which are' to 'be controlled by the shock absorber.l The iower head I5 is suitably formed for connection with the other of the elements movements of which are to be controlled by the shock absorber.

Threaded onto the head I4 is a cap 20 which cooperates with said head to provide a chamber 2|. 'I'he piston rod I8 may be packed or ysealed in the same manner as illustrated and described in my copending application, Serial No. 6551211, so that any liquid which may escape from the cylinder I0 along the piston rod collects in said chamber 2| and escapes therefrom to the reservoir .I1 through a duct 22 formed in the head Il. It has been found, however, that a more desirable arrangement is 'to provide for a small amount of more or less free ow of liquid from the pressure chamber a along the piston rod I8 into the chamber 2| and to provide a tight seal preventing escape yof liquid from said chamber 2| along the piston rod through the bore in the cap 20 through which the piston rod.` extends. Accordingly, a packing ring 2li*i of leather or other suitable material is disposed within a recess -in the cap 20 in surrounding relationship to the piston rod I8 and below this gasket, also in surrounding relationship to the piston rod, and extending through the chamber 2| into a chamber 2|*l in the head Il,

disposed a follower 22*t of any` suitable material which is urged against the packing ring 20'l by a spring22h t aintain a tight "sealing engagement of said acking ringwith the "piston rod. The follow'ev 22EL more or less loosely` ts the piston rod so that lliquid may iiow morel or less freely through the piston rod bore therein, and said follower is provided with one or more small ducts 22 for the outlet into the chamber 2 In of liquid which escapes along the piston from within the operating chambers of the shock ab. sorber always yfinds its way to the top'ofv the vliquid inan effort to 'escape therefrom. Consequently, any air which may remain in the pressure chambers of the shock absorber when the liquid along the piston rod into the chamber 2i,ib and from said chamber by way of chamber 2| through the duct 22 into the reservoir I? where it does not affect the operation of the shock absorber due to the relatively large capacity of said reservoir and to thefact that the same need not be entirely lied withliquid. As aforesaid, the

amount of liquid which may 'escape along the piston rod isrelatively small so that such escape of liquid does not in any appreciable way affect the shock absorbing functions of the shock absorber. Moreovenjsince only a small amount of liquid escapes along the piston rod and since this liquid may return to thereservoir I1 as rapidly 1 head YIILserves effectively as a seal to prevent sucking back into the pressure'chamber a of air which has been purged from said pressure cham--y e y 2,036,623 v 'a central here in the head u is a piston rod ls ber. the present shock absorber always is self-purging of air and therefore is devoid of y those objectionable features of operation of'prior shock absorbers which are directiy traceable to air pockets affecting the operation lof the valves and other parts thereof. `A check valve 23 preferably is provided to permit flow of liquid from the chamber 2| the reservoir I1 and to prey vent reverse flow of the liquid.

1' A boot 24 of leather or-othersuitable material i as illustrated and described in my said copending application, Serial No. 631,211.

The lower head I5 4is provided With a horizontal bore 25 which opens at its outer end through the side of said head and at its inner end into the bottom portion of a vertical duct 26 which, at its upper end, opens into the bottom of the cylinder III. The inner end portion of the bore 25 is of lreduced diameter and is threaded and receives the inner, threaded end of a valve, designated generally as A, including cylindrical valve casing 21 having a head 28 which seals, through a gasket 29, against the outer face of the head I5. Ihe said valve casing, between its ends, thus is surrounded by a space 3U which is in communication with the reservoir I1 through a duct 3i formed in the head I5.V ff l Above the bore 25 the ducts 26, 3| are connected by-a duct or passageway 32 ywhich is controlled by a check valve 33, ,said valve being arranged to close in the direction of the duct 3| and to open in the direction of the duct 25 so that liquid cannot escape from the cylinder I0 to the vreservoir I1 but may flow from saidhreservoir to vsaid cylinder.

A spring 34 interposedbetween the vaive 33 and a plug,35 threaded into the head I5 maintains said valve'l, normally seated., the plug being exposed at the sideA of the head so that it may readily be removed Whenever desired to permit removal of said valve.

The inner end of the valve casing 21 is suit-l ably shouldered as indicated at 36 and provided with an opening 31, a centrally bored plug 38 being threaded into the inner end of said valve casing, for example, to provide said shoulder and cpening. Longitudinally slidablewithin said valve casing is ahollow spool valve 3e the outer end portion of which snugly engages the casing and the inner end portion of which is of reduced external diameter. 'ihis spool valve is closed at its inner end and is open atits outer, end, and

by aecoil spring 40 is lurged constantly inward to its innermost limit of movement in whichits closed inner end seats against the shoulder 36 and closes the opening 31.

Carried by and extending inwardiy from the head 28 of the valve casing 21 is a 4I having at its inner end an inwardly tapered head 42 the greatest 4diameter of whichis slightly less than the internal diameter of the inner end portion of the spool 'valve 39. When the spool valve is at its limit or' inward movement seating against the shoulder 36, the outer end portion of greatest diameter of the head 42 is disposed somewhat outwardly of the outer end portion'of the inner, reduced internal diameter portion of the spool valve. Formed through the reduced, inner end portionof the spool valve is an opening or openings .43 providing communication between the interior of said valve portion and the an- -nular space surrounding the same, while formed through the valve casing 21,*near its outer end is an opening or openings 44 providing communication between the interior of said valve casing and the annular space surrounding the same. Formed in the head I5 is a second horizontal bore 45 which opens at its outer endthrough the side of said head and at its inner end intov the bottom portion of a second vertical duct 46 which, at its upper end, opens into the bottom of the cylinder I0. The inner end .portion oi the bore 45 is of reduced diameter and is threaded and receives the inner, threaded end of a cylindrical valve casing 41 of a second valve designated generally as B, said casing 41 having a head 48 which seals, tijarough a! gasket 49, against the outer `face of the head I5. The said valve casing between its ends thus is surrounded by a space 50 which is in communication through a duct 5I with the liquid passageway I6 between th cylinder I8 and the tube I2. y

Above the bore 45 the ducts 46 and 5I are connected by a ductor passageway 52 which is j controlled by a check valve 53, said valve being arranged to close in the ldirection of the duct 46 and to open in the ldirection of the duct 5I. A spring 54 interposed between the valve 53 and a plug 55 threaded into the head I5 maintains said valve normally seated, theplug being exposed at they side of the head so that it is readily removable to permit access to or removal of said valve. i

The head 48 of the valve casing 41 is relatively thick and. is provided with a central bore 56 which opens into the interior of said valve casing and which -is surrounded by a shoulder 51 dening the outer end of the bore oi' said casing.

Ducts 58 aiord communicationv between the boreA 56 and the annular space 58 surrounding said valve casing 41.

Longitudinally slidable within the valve casing 41 is a hollow spool valve 59the inner end portion of which snugly engages the casing and the outer end portion of' which is oi reducedexternal diameter. This spool valve is closed at its outer end and is open at its inner end and by a coil spring 60 is urged constantly outward to a position in which its closed outer end seats against the shoulder 51 and closes the bore 56.

'suitably carried by and extending outwardly from the inner end portion of the valve casing 41 is a pin 6I having at its outer en d an out-A wardly tapered head 62 the greatest diameteroi' which is slightly less than the internal diameter of the outer end portion ofthe spool valve 59. When the spool valve is at its limitbf outward movement seating against the shoulder 51, the inner end portion of greatest diameter of the head 62 is disposed somewhat inwardly of the inner end portion of the reduced internal diameter portion of the spool valve. In the present instance the pin 6I is carried by a plug 63 which is threaded into the inner end of the-valve casing 41 and which is bored as indicated at 64 to provide constantcommunication between the inner end portion of said valvecasing and the duct 46. In the spool valve 59 isan opening or openings 64 which provide communication between the interior of said valve and the annular space surrounding the inner end portion thereof.

Formed in the upper head I4 is a horizontal bore 65 which, at its inner end, is in communication with the top of the cylinder I 0 through a duct 66, and which, at its outer end, opens through the side of said head, The inner end lportion of this bore 65 is'oi reduced diameter and is threaded and receives the inner, threaded end of a cylindrical valve casing 61 of a third valve designated generally as C, said casing 61 having ahead 66 which seals, through a gasket 68, against the outer face of .the head I4. The

'provide communication between the inner and the outer end portions, respectively, of said valve casing and the annular space 10 surrounding the same.

Reciprocal within the valve casing 61 between the openings 14, 15, is a piston 16 which, at its inner end carries a pin 11 -having 'an inwardly tapered head 18 the greatest diameter of which is slightly less than the diameter of the opening 13. A spring 19 interposed between the head 66 and the piston 16 tends constantly to urge said piston inwardly, and a spring 80 interposed between the plug 12 and said piston tends constantly to urge said piston outwardly, said springs co; operating to maintain said piston normally in a position approximatelyl midway between the openings 14, 1 5 with the tapered head 18 disposed partially within the opening 13. Preferably. the inner or smaller end ofthe tapered head 18 terminates in a circular ange or enlargement 18e which is o1' only slightly less diameter than the opening 13 and which substantially closes said opening when the head 18 is in its normal position substantially as shown in Fig. 2. The valve constituted by the tapered head'16, instead of permitting practically .free ow oi' liquid through the. opening 13 at the beginning oi any period of operation of lsaid valve, as would be the case if the ange or enlargement 18EL were omitted, manifestly is pressure operated at the start of any period of operation, which provides for smoother action of the shock absorber as affected in its operation by said valve.

Formed through the cylinder I 0` substantially midwaybetween the ends thereof is an opening or openings 8| which is or are covered by the piston II when the latter is in its normal position substantially midway between the ends of the cylinder and which are uncovered when said piston is movedv either downwardly or upwardly from its normal position.

Assuming that the shock absorberis charged with oil or other liquid filling the cylinder I0 and the passageway I6 and partially lling the reservoir I1, and that the shock absorber is interposed between the axle and the spring supported chassis or body of a motor vehicle, for example, it has four distinct phases of operation; viz., (1), compres.

sion above normal as when an obstruction in the roadway is encountered and the cylinder I0 is moved upwardly relative to the piston II; (2), rebound above normal or downward movement of the cylinder relative to the piston following compression above normal; (3), rebound below nore the piston within the chamber b/is subjected to into and through the duct 46 to the bottom of pressure. The check valve 33 obviously remains closed and the check valve 53 opens, permitting iiow of liquid from the bottom of the cylinderv III through* the ducts 46 and 52 into the passageway I6 and through the openings 8 I, uncovered by the relative movement of the. cylinder and piston, into the cylinder space or chamber a above the piston. Because of the presence of the piston rod I8 in the chamber a said chamber is of less capacity than the chamber b. Consequently, upon -movement of the piston I I and the head I5 toward each other, more liquid isforced from the chamber b than can be accommodated by the chamber a. The only avenue of escape for the surplus liquid obviously is through duct 25, the valve casing 21 and the duct 3I into the reservoir I1.

.The pressure of the liquid against the closed end of the spool valve 39 results in said valve being moved loutwardly with consequent flow of the surplus liquid through the opening 31 Ainto the space surrounding the inner end portion of said spool valve, through the openings 43 in the spool -valve to the interior thereof, thence around the tapered 4head 42 into the casing 21, from said casing through the openings 44 therein into the space and from said space through the duct 3i into the reservoir I1. KAs the spool valve 39is moved outwardly the space between the tapered head and the interior of said spool valve diminishes. v Consequently, free relative movement of the piston II and the head I5 toward each other is permitted initially, but thereafter the flow of the liquid is throttled by the metering head 42 so that the shock is gradually and eiectively absorbed, this obviously holding true no matter how suddenly or severe the shock may be.`

'I'he second phase of operation, rebound above normal, occurs following compression above normal and results from the compressed -vehicle springs acting to move the piston and the head I5 relatively apart after-the obstruction in the roadway has been passed. At the beginning of this phase of operation the piston II -is presumed to be disposed within the chamber b below the openings 8l. Under such conditions, as the piston II and the head I4 move toward each other, the liquid above the piston within the chamber a is subjected to pressure 'and flows from said chamber a through the openings 6I into and through the passageway I6 to the duct 5I, being prevented from directly entering the bottom of the check valve 53 and being required, therefore, to

flow to the bottom of the cylinder I0 through the valve casing 41. 'I'he 'pressure produced in the passageway I6, duct 5I, space 60. ducts 58 and bore 55- results in the spool valve 59 being moved outwardly, whereupon the liquid is -permitted to flow into the space surrounding the outer end portion of the spool valve 59, through the openings 64' into the .interior Iof said valve, around the tapered head 62 into the cylinder 41, and thence the cylinder I6. 'Ihevalve in the head I4 does not function during this phase of operation because the pressure is balanced to either side of the` piston 16. Since the chamber a is'of less capacity than the chamber b, not enough liquid is forced from the chamber a during "rebound above normal to ll the chamber b. Consequently, the check valve 33 opens and enough liquid is drawn from the reservoir I1 through the ducts capacity of the chamber'b. AThe spool valve 39 remains inoperative because it closes in the direction of the bottom ofthe cylinder I0. The spool valve 53 and the tapered head 52 cooperate during the rebound above normal phase of operation to control the flow of the liquid in the same manner that the spool valve 39 and the tapered head 42 cooperate to control the ow of the liquid yduring the compression above normal phase of operation, so that rebound above normal shocks are gradually and effectively absorbed.

Thev third phase of operation, rebound below normal, occurs when the piston II is in its normalposition approximately midway between the ends of the cylinder I0 and when, for example, there is encountered a. depression in the roadway. When the vehicle wheels drop into the depression the axle and chassis movevapart withV the result that' thepiston II and the head move relatively toward each other. Pressure therefore is generated in the cylinder space or v openings 14 into the annular space 10, from said` space through the duct 1l to the passageway i6 and fromH said passageway through the uncovered openings 8| into the cylinder space or chamber b below the piston Il. Depending upon the suddenness of the movement of the piston II and the. head I4 toward each other and therefore upon the amount of pressure generated, the piston 16 is moved more or less outwardly against the spring 19 so that the effective area of -the space between the head 13 and the wall dening the opening 13 is varied to throttle the ow in a manner to gradually and effectively absorb any shock incident to the rebound below normal phase of operation. In this connection, due to the openings 14, 15 being located at opposite ends of the piston 16, it is apparent that said piston is subjected at opposite ends thereof to equal or balanced pressures so that the amount of movementof said piston to open or close the valve constituted by the tapered head 18 is directly proportioned to the pressure generated. Since not enough liquid is forcedfrom the chamber a to fllthe chamber b during movement of the piston II and the head I4 toward eachother, the

check valve 33 opens and liquid in suiiicient quantity to maintain the chamber b filled is drawn from the reservoir I1 through the ducts 3| 'and The fourth phase of operation, compression below norma occurs following rebound below normal and resultsin part from the distended vehicle springs acting to move thevehicle axle and chassis toward Aeach other and in part to the vehicle wheels leaving the depression and tending to force the axle upwardly relative to the chassis. At the beginning of this phase of operation the piston II is presumed to be disposed within theV chamber a above the openings BI. Under such conditions, as the piston Il and the head I5 are moved toward each other the liquid below the piston within `the chamber b is subjected to pressure and ows from said chamber b through theopenings 8| into and through the passageway I6 to and through the duct 1I to' the space 10 surrounding the valve casing 61, thence yf through the duct 66 to the space or chamber a above the piston II, the flow being metered by the tapered head 'I8 cooperating with the wall surrounding the opening I3 so that return of the vpiston II to its normal position following the rebound below normal phase of operation is gradual and results in the shock being eifectively absorbed. Since, during the compression below normal phase of operation, more liquid isfforced vfrom the chamber b than can be accommodated by the chamber a, the spool valve 88 opens and surplus liquid flows around and through said valve to the reservoir I1.

In Figures 6 and 7 of the drawings is illustrated an embodiment of the invention in which the general shock absorber construction and mode oi' operation is similar to the embodiment of the invention illustratedin Figs. 1 to 5 and described in the foregoing. but wherein a somewhat different valve combination is utilized to control the flow of the liquid.

Referring to Figs. 6 and 7, it will be observed that the valves A', B' are the same as the valves A and B, respectively, of the Figs. 1- to 5 embodiment of the invention, but that the check valves understood, of course, that the upper part of the shock absorber, including the valve C, remains as illustrated in Figs. 1 and 2.

Referring morel particularly to Figs. 6 and 7, wherein the same reference characters are, for the sake of simplicity, employed to designate parts which in no way differ from corresponding parts illustrated in the Figs. 1 to 5 embodiment of the invention, it will be observed that the space 30 surrounding the casing 21 ofthe valve A' is not in communication with the reservoir I1 as in the Fi'gs. 1 to 5 embodiment of the invention, but, on the contrary, is in communication with the liquid passageway I6, through a duct 3I'; that this duct 3i does not communicate with the bottom of the cylinder I8 through a check` valve controlled passagewayas in the Figs. 1 to 5 embodiment of the invention, and that the space 50 surrounding the casing 41 of the valve B' is in communication with the liquid passageway I6 through' a duct 5I as in the Figs. 1 to 5 embodiment of the invention, but that said duct 5| is not in communication with the bottom of the cylinder I0 through a check valve controlled passageway as in the Figs. 1 to 5 embodiment of the invention.

Further, it will be observed that the valve D comprises a plug 55 which is threaded into and closes the outer end portion of a horizontal bore 52 in the head I5; that .the bore 52 intersects the duct 26 through which communication is afforded between the bottom of the cylinder I8 and the inner end of the valve A'; that the plug 55' is provided with a bore 82 closed at its outer end and opening at its inner end through the inner end of said plug; that openings 83 provide communicationbetween said bore 82 and an annular channel 84 surrounding the Yplug 55'; that said channel, and consequently the bore 82, is in communication with the reservoir I'I 'through a duct 85 formed in the head I5; that slidable within the inner end portion of the bore 52' is a spoollike valve 86 which constantly is urged outwardly into seating engagement with the inner end of the plug 55' by a light coil spring 8l; that Isaid ybore 82 of the plug 55', and that within said bore 88 is a check valve 89 which is maintained nor'- mally closed by a spring 90 and which permits flow of liquid from the inner end of the bore 52' into the bores 88 and 82 and consequently to the reservoir Il under certain conditions when the valve 86 is closed or, in other words, when said lvalve 86 is sealed against the inner end of'the plug 55', but which denies reverse flow of the liquid. l

The Figs. 6 and 7 embodiment of the invention operates as follows: As compression above normal takes place; i. e., upon movement of the piston II and the head I5 toward each other the liquid below the piston within the chamber b is subjected to pressure and obviously is prevented from escaping through the valve B' because this valve is a one-way valve denying flow of liquid from the chamber b to the passageway I6. Therefore, the only avenues of escape for the liquid are through the valves A' and D. 'I'he strength of the spring 90 maintaining the ball check valve 8,9 normally closed is such that the pressure required to open said check valve 88`is above the maximum operating pressure `of the valve A. Consequently, check valve 88 remains closed under normal conditions and valve A' opens, permitting a metered flow of the liquid from the chamber b through the duct 8l into the passageway, I6 and thence to the space aA above, the piston. However, ii', for any reason, the movement of the piston II is very sudden, resulting in the building up of an excessively high pressure in the chamber b, the valve 88 may open to relieve such'pressure and thus cushion the shock. Since more liquid is discharged from the chamber b than can be accommodated bythe chamber a there comes a time during downward movement of the'piston when the liquid below the same, unless released, would constitute a solid abutment preventingV further vdownward movement of the piston. However, before this condition is encountered the pressure generated results in opening of the check Valve 88 with consequent discharge of the excess liquid into the reservoir y .l

As rebound above normal takes place; i.'e., upon upward movement of the piston following the compression above normal period oi' operation just recounted, the liquid above the piston is subjected to pressure and flows from the chamberA a through the ports 8| to the duct 5I and through the valve B and thence to the chamber b at the bottom of the cylinder I8 as in the Figs. 1 to 5 embodiment of thel invention. Since the chamber a is of less capacity than the chamber b, not enough liquid is forced from the chamber a to ll the chamber b. Consequently, the valve 86 is drawn open against the light spring 81 and liquid in an amount to ll the chamber b is drawn from the reservoir I'I through the duct 85'and through the bore 82 of l 86 which loosely vshock absorber will be clearly n that the advantages thereof will he appreciated.

below normal phase of operation, the operation is the same Aas recounted in connection'with the Figs. 1 to 5 embodiment oi the invention and as just set forth in connection with the "compres- A sion above normal phase of operation.

From the foregoing description considered in connection with the drawings it is thought that the construction Yand operation of the present understood and However, it is desired to emphasize that all valves are readily and easily vremovable for adjustment, cleaning, replacement or for any other reason, individually andwithout in any way requiring `dis-assembly of Y.any other part or parts of the f shock absorber; that a fording all necessary lair and liquid space'Y so that V,the necessity of anybreather valve for said reservoir is avoided; that the spooivalves are duplicates of one another and may be used interchangeably, which is of'decided advantage from an economical production standpoint, and that the general construction is simple and rugged and embodies parts which are strong and durable' and which are not likely to become broken or damaged or to get out of order. While only certain specific embodiments of the I 'Y invention have been illustrated; and described, itA

l reservoir, heads closing the ends of said cylinder,

tubejand casing, a piston rod extending from the piston through one of said chambers andi one of said'heada'and valves controlling flow of liquid between the chambers through said passageway and between the chambers and said reservoir.

2. A hydraulic shock absorber comprising a cylinder, a piston reciprocal :Within said cylinder I and havinga normal position between the ends thereof dividing the cylinder into separate pressure chambers, a tube surrounding the'cylinder in spaced relationship thereto to provide a laiuid passageway, a casing surrounding the `tube in spaced relationship thereto to 'provide a liquid reservoir, heads closing theends of said cylinder, tube and casing, a Vpiston rod extending from the piston through one of said chambers andone of said heads, said cylinder having an opening intermediate its ends which is' closed by said piston ywhen thelatter is in its normal "position and which is uncovered when the piston is move-:i into either pressure chamber toafford direct Ycomniunication between said passageway andthe other pressure chamber, and valves controlling flow of liquid between the chambers through said passageway land opening and between the chambers and said reservoir.

3. A hdrauuo shook absorber as set forth in claim 1 in which all of the liquid control valves are carried by said heads and are individually removable without requiring' disassemblyof the heads from the cylinder, tube casing.

4. A hydraulic shock absorber Ygas set forth liquid storage reservoir fof"exceptionally-large capacity is provi-ded aff aosoas claim 2 in` which all of the liquid control valves are carried byA said heads and are individually removable without requiring disassemblyv of the headsfrom thewcylinder, tube and casing.

5. A hydraulic shock vabsorber as set forthin' giclaim -lY in which the head having the-pistonnrod extending therethrough is providedwith a Y, chamber for the collectioncf'any liquid which Ymay leak along'said piston rod; and inwhich a V*duct' inY said head provides communication bentween said liquidv collection chamber andzfithem liquid reservoir.

6. A shockabsorber as set forth in. claim.-

whichfthe head havingthe piston rod extending therethrough is provided with a chamber. for

the collection of any liquid Awhich may leak along-`- said piston rod, and in which'a duct insaid head provides communication between said liquid collection chamber andthe liquid reservoir.

7. A hydraulic shock absorber .comprising a cylinder, a piston reciprocal within said cylinder and'having a normal position between the endsfthereof `dividing the cylinder into separate pressure chambers, va tubesurrounding the cylinder in spaced lrelationshipvthereto Y'to provide a liquid passageway, a casing surrounding said tuberin spaced relationship Ythereto ito provide a liquid reservoir, heads closing the ends of said cylinder, tube and casing, a piston rod extending from said pistonY through one of said chambers and one of said heads, the cylinderhaving 1an opening intermediate its ends which is closed by said piston when the latter is in its normal position and which is uncovered whenthe piston is moved into either pressurej chamber to afford direct communicationv between said passageway andthe other pressiire chamber, a check valve within one G Said heads operable upon movement of the piston from its normal position into one bfsaid pressure chambers topermit flow ofi-,the liquid from said pressure chamber into the other pressure Ychamber andy to prevent reverse flow of theliquid, anda second valve -lilithinthe same .head controlling ow of liquid from said first mentioned pressure chamber intoA said reservoir.

, a. A hydrauuo shook absorber as set forth in claim 'l in which; the second mentioned Yvalve is constructed to operate under a rising pressure in the first mentioned pressure chamber to proy gressivelynretard flow of liquid from said chamsure chamber to its normal position to control now of liquid from the second mentioned-chamioer through thelpassageway to the first mentioned chamber, said fourth valve being operable under a rising pressure in the second mentioned chamber to progressively retard iiow of liquid from the second mentioned pressure charnber to the first mentioned chamber. v

10. A hydraulic shock absorber as set forth in claim '7 in which the secondgmentioned valve :is operable as a check valve to permit flow of liquid from the first mentioned pressure chamber to the reservoir and to prevent reverse flow of the liquid,and in which saidsecond mentioned valve'is constrLcted to operate under a in rising pressure in therst mentioned pressure 75 i chamber to progressively retard ow of the liquid from said chamber into the reservoir.

11. A hydraulic shock' absorber as set forth in claim 'l including a second check valve within the same head as the rst check valve permitting ow of liquid from the reservoir into the rst mentioned chamber, and a fourth valve within the same head operable upon return movement of the piston from the first mentioned pressure chamber to its normal position and under a rising pressure in the second mentioned pressure chamber to progressively retard flow of liquid from the latter pressure chamber to the rst mentioned pressure chamber, said fourth valve being operable to permit ilow of liquid from the secondmentioned pressure chamber to the rst mentioned pressure chamber and to prevent re- -verse ow of the liquid.

12. A hydraulic shock absorber comprising a cylinder, a piston reciprocal within said cylin-V trolling ow of liquid from the second mentioned `pressure chamber'to the-first mentioned pressure chamber, and a single-unit, double check valve controlling flow of liquid in both directions between one of said pressure chambers and said reservoir.

13. A hydraulic shock absorber comprising a cylinder, a piston reciprocal within saidcylinder and having a normal position between the ends thereof dividing the cylinder into separate pressure ch-ambers,the cylinder having an opening, means providing a passageway which, in conjunction with said opening, affords communication between said pressure chambers when the piston is moved in either'direction from its normal position, means providing a liquid reservoir, a .liquid metering valve controlling ow of liquid from one of the pressure chambers to the other, a second liquid metering valve controlling now of liquid from the second mentioned pressure chamber to the first mentioned pressure chamber, and a single-unit, double check valve controlling flow of liquid in both directions between one of said pressure chambers and said reservoir, said single-unit valve comprising a hollow member slidably mounted to close under the influence of pressure generated in one of the pressure chambers to prevent escape of liquid from said pressure chamber to the reservoir, and a check valve within said hollow member permitting flow of liquid therethrough to the reservoir and denying reverse flow of the liquid.

1.4. A hydraulic shock absorber comprising a cylinder, a piston reciprocal within said cylinder and having a normal position between the ends thereof dividing the cylinder into separate pressure chambers, the cylinder having an opening, means providing a passageway which, in conjunction with said opening, affords communication between said pressure chambers when the piston is moved in either direction from its normal position, means providing a liquid reservoir, liquid metering valve means controlling flow of liquid from each pressure chamber to the other pressure chamber, and a single-unit double check valve permitting substantially free flow of liquid from the reservoir to one of the pressure chambers and permitting ow of liquid from the same pressure chamber to the reservoir only under a pressure in excess of the maximum operating pressure of said metering valve means.

15. A hydraulic shock absorber comprising a cylinder, a piston reciprocal within said cylinder and having a normal position between the ends thereof dividing the cylinder into separate pressure` chambers, the cylinder having an opening, means providing a passageway which, in conjunction with said opening, affords communication between said pressure chambers when the piston is moved in either direction from its normal position, means providing a liquid reservoir, liquid metering valve means controlling flow of liquid from each pressure chamber to the other pressure chamber, and a single-unit double check valve permitting substantially free flow of liquid from the reservoir to one of the pressure chambers and permitting flow of liquid from 'the same pressure chamber to the reservoir* only under a pressure in excess of the maximum operating pressure of said metering valve means, said single-unit valve comprising a member slidably mounted to close under the inuence of pressure generated in the last mentioned pressure chamber thereby to prevent flow of liquid under relatively low pressure from said last mentioned pressure chamber to the reservoir, said member having a duct extendingtherethrough, a check valve denying flow of liquid through said duct from the reservoir to the last mentioned pressure chamber and permitting reverse ilow of the liquid, and a spring maintaining said check valve closed except under pressure in excess of the maximum operating pressure of said metering valve means. 4

16. A hydraulic shock absorber comprising a cylinder, a piston within said cylinder and having a normal position between the ends thereof dividing the cylinder into separate pressure chaml bers, heads closing the ends of said cylinder, a pis` ton rod extending from said piston through one of said heads, means providing a. chamber into which liquid and air escaping along said piston rod may collect, means preventing escape of liquid from said chamber along that portion of the piston rod disposed outwardly of said chamber, said piston rod inwardly of said chamber extending loosely through the head so that liquid and air in relatively small' amounts may escape to said chamber, a liquid reservoir, means providing communication between said chamber and said reservoir, said chamber being devoid of communicay tion with the cylinder except through the clearance space between the piston rod an-d the head through which said rod extends, and valve means controlling flow of liquid between the pressure chambers and between the latter and said reservoir.

NEVIN S. FOCHT. 

